Hello there, @damond. I'm here to share some details about importing accountant changes in QuickBooks Online (QBO).
In addition to Fiat's questions above, could you tell me if you've already invited your accountant to your QBO company? This process will let them access your file to review your books, make necessary corrections, undo the entire reconciliation, etc. If you haven't yet, you can use this article for the detailed process: Add accountant users in QuickBooks Online.
Also, the Import Accountant Changes option is only available if you're using the QuickBooks Desktop (QBDT) product.
On the other hand, you can utilize the import feature in QBO, to upload data such as bank transactions, name lists, invoices, etc. Please check this page for a detailed guide: Common questions about importing data to QuickBooks Online. This also includes the list of file formats supported by the program.
Then, I've added this link to serve as your reference in making sure your data is categorized correctly: Categorize and match online bank transactions in QuickBooks Online.
Please leave a reply below with any other details you can add. I'll be here waiting for your response. Have a good one and keep safe.